Experimental Bucklings of Heavy Water Moderated Lattices of Natural Uranium Metal Rod Clusters

Studies performed in the Process Development Pile of the Savannah River Laboratory have provided precise measurements of the material bucklings of a number of D₂O-moderated lattices of natural uranium metal rods over an extended range of fuel assembly sizes and lattice pitches. The 1-in. uranium rods were clad with 0.032 in. of aluminum. Fuel assembly sizes varied from single rods to clusters of 3, 7, and 19 rods (0.09 to 1.81 kg U/cm) and lattice spacings from 7.00 to 21.00 in., covering a range of moderator-to-fuel volume ratios from 10.23 to 161.53. A few lattices were studied at different D₂O purities, in loadings of different sizes, and in reflected loadings.